Sterling shot up around a cent against the dollar and government bonds tumbled as many investors had expected a bigger expansion of the eight-month-old programme to buy assets, mostly UK government bonds, with newly-created money.

The BoE, which also left interest rates unchanged at a record low of 0.5 percent as expected, said the bond-buying would take another three months to complete and analysts said that would probably mark the end of the programme.

We suspect that this will be the final extension to the QE programme unless the economy suffers a major relapse in 2010, said Howard Archer, economist at IHS Global Insight.

While the BoE noted that numerous surveys had indicated that a pick-up in the economy was in sight, it still believed the prospect was for a slow recovery in the level of economic activity.

That will continue to bear down on inflation for some time to come, offset in the short run by the impact of the past depreciation of sterling, the BoE said in a statement.

Two-thirds of analysts polled by Reuters had predicted the central bank would expand its asset-buying scheme, but opinion had been split evenly on whether the increase would be 25 billion or 50 billion pounds.

The Bank seems to be weaning the market off QE and we strongly suspect that -- barring any further negative surprises to economic growth -- this will be the last instalment of the programme, said George Buckley, economist at Deutsche Bank.

Britain's economy remained mired in recession in the third quarter. The United States, Germany and France have already started growing again.

The European Central Bank will make its own interest rate decision at 1245 GMT and on Wednesday the U.S. Federal Reserve signalled that it would keep interest rates at near zero for some time to come.

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